1. Field of the Invention
The present invention relates to a substrate for use of an ink jet recording head, a method for manufacturing such substrate, an ink jet recording head, and an ink jet recording apparatus.
2. Related Background Art
The ink jet recording method which is disclosed in the specification of U.S. Pat. No. 4,723,129 or 4,740,796 makes it possible to perform a highly precise recording in high quality and density at higher speeds. With this method, it is easier to record in colors by use of a compact recording apparatus. Particularly, in recent years, this method has attracted much attention. For the typical example of an apparatus that uses this method, it is arranged to utilize thermal energy for discharging recording liquid or the like (hereinafter referred to as ink). The apparatus is provided with a thermal activation portion to enable heat to act upon ink. In other words, for each of the ink flow paths, there are arranged a pair of wiring electrodes and an electrothermal converting member connected with the wiring electrodes. This member is formed by the heat generating resistive layer to generate heat in an area between the wiring electrodes and heat ink abruptly to foam on the thermal activation portion by the utilization of the thermal energy generated by the heat generating resistive layer, and discharge ink by means of the foaming thus created.
Now, in this respect, many proposals have been made as to the materials and structure of the heat generating resistive layer of the ink jet recording head. For example, the one disclosed in the specification of Japanese Patent Laid-Open Application No. 7-125218 is a heat generating resistive member of Ta type or the one disclosed-in the specification of U.S. Pat. No. 5,169,806 is a heat generating resistive member that uses polysilicon. Also, in order to arrange the pitches of the heat generating resistive members in higher density, it has been proposed to arrange the wiring below heat generating resistive members so as to eliminate the wiring between each of the heat generating resistive members as disclosed in the specification of Japanese Patent Publication No. 2034786, for example.
However, for the conventional structure that uses polysilicon heat generating resistive members, there is a problem encountered that if it is attempted to use the wiring pattern immediately below the heat generating resistive members in order to arrange them in higher density, the conventional structure cannot be adopted practically from the manufacturing point of view.
In other words, the wiring which is usually used is Al or Al alloy in general, and the fusion point thereof is approximately 580xc2x0 C. Here, on the other hand, the polysilicon formation temperature is beyond 600xc2x0 C. as practicably adopted for the general semiconductor process. If this high temperature process is required subsequent to having formed Al wiring, the Al is diffused eventually.
Because of a problem of the kind, the Al or Al alloy wiring cannot be arranged below the layer using polysilicon as the heat generating resistive members.
The present invention is designed with a view to solving the problems discussed above. It is an object of the invention to provide the vertically turn-up wiring structure capable of arranging heat generating resistive members in higher density, while using polysilicon for the heat generating resistive members.
It is another object of the invention to provide a method of manufacture which makes it possible to arrange the connection with metallic wiring for use of current supply for the vertically turn-up wiring structure of the heat generating resistive members using polysilicon.
Here, with the provision of means given below, it is possible to achieve these objectives.
In other words, the substrate for use in an ink jet recording head, which is proposed herein by the present invention, comprises a plurality of heat generating resistive members formed on the substrate; a wiring pattern formed to be electrically connected with the heat generating resistive members; and a protection film formed on the heat generating resistive members and the wiring pattern to protect them from ink, and then, a vertically turn-up wiring structure is formed with an insulation film formed on the substrate, and one side of the wiring connected with the heat generating resistive members is arranged immediately below the heat generating resistive members in a width and a length larger than that of heat generating resistive members with the insulation film between them. For this substrate, the heat generating resistive members and the wiring positioned immediately below them are formed by polysilicon having impurities in different densities. Here, each sheet resistance of the heat generating resistive members is 70 to 300 xcexa9/xe2x96xa1, and the polysilicon sheet resistance of the wiring positioned immediately below them is 1 to 20 xcexa9/xe2x96xa1. Also, the vertically turn-up portion of a plurality of vertically turn-up wiring structures using polysilicon for the heat generating resistive members and the lower layer wiring with the insulation film between them is arranged to form a step higher than the substrate portions positioned on both sides thereof. Further, each thickness of the heat generating resistive members and the wiring positioned immediately below them is 50 to 1,000 nm.
Also, a method, which is proposed herein by the present invention for manufacturing a substrate for use of an ink jet recording head, which is provided with a plurality of heat generating resistive members formed on the substrate; a wiring pattern formed to be electrically connected with the heat generating resistive members; and a protection film formed on the heat generating resistive members and the wiring pattern to protect them from ink, and a vertically turn-up wiring structure being formed with an insulation film formed on the substrate, and one side of wiring connected with the heat generating resistive members being arranged immediately below the heat generating resistive members with the insulation film between them, comprises the step of forming metallic wiring connected with the portion having the heat generating resistive members and the wiring positioned immediately below them subsequent to the formation of the portion. Then, the metallic wiring used for this method is Al or Cu individually or an allow thereof.
Further, the objectives of the present invention are achieved with the provision of an ink jet recording head comprising the substrate described in the preceding paragraphs, and the ink flow paths arranged corresponding to the heat generating resistive members, as well as with the provision of an ink jet recording apparatus which comprises such ink jet recording head for performing recording by discharging ink from the discharge ports thereof in accordance with recording signals.